The present invention relates to annual crop straw and stalk fibers which have suitable properties for use in paper, paperboard and related products made therefrom, disposable dinner plates, cups, and bowls, molded pulp containers, and food trays and food handling containers, clamshell containers, tissue and toweling, and absorbent products such as diapers, roligoods, and feminine hygiene articles. Other uses include reconstituted cellulose such as rayon and electronic article packaging. Up to this time, farmers have the alternatives of tilling part of the stalk and straw back into the soil and disposal of the excess. Only a portion of the stalks can be reasonably tilled back into the soil each year. Therefore, the farmer is faced with disposal of large quantities of the waste stalk and straw after harvesting the food crop. Straw and stalk have been burned in the past, but this is obviously not an environmentally friendly process due to the air pollution created. The use of straw and stalk fibers in high value products also represents an opportunity to the farmer to recover additional income per acre of crop land without impacting the food crop supply.
A significant amount of effort has been undertaken to use annual crop waste straw such as wheat, oats, soy, corn, sugar cane, and rice in paper and paperboard products. The opportunity in this area is to use waste materials from agricultural products which decreases need and cost of waste disposal, increases value to the fanner, and provides a viable replacement for wood pulp, thereby saving trees. Also, the use of the waste straw and stalks does not impact the food supply. This approach represents the next level of “Green” or environmentally responsible manufacturing. Also, the annual crop fibers have the potential of providing enhanced properties compared to wood pulp. Wheat straw has been made into pulp fibers, and wet laid into paper products. Much work has been done in Canada and United States as well as China to process Wheat into paper for printing. In Canada, the Alberta Research Center has taken Wheat straw from China and processed it into printable paper called Wheat Sheet and it was used to print a publication of National Geographic in 2008. The Wheat Sheet had 20% wheat fiber and 80% wood pulp fiber. The pulping and recovery systems proved to lack commercial economic viability. Also, chlorine bleaching is an environmentally undesirable process. The present invention relates to processes and applications that do not require chlorine bleaching to be suitable for paper, paperboard, and related products, and absorbent product end uses.
Reference Application U.S. #20070199669 Yang:
The reference patent application relates to processing of annual crops for the formation of long, coarse fiber bundles for use in textiles and composites. This reference teaches towards maintenance of high coarseness, long fiber bundles from annual crop straw and teaches away from formation of individual fiber cells, low coarseness and shorter fibers consisting of small multiple cells bonded in the manner of the original straw which are unsuitable for textile use. The fibers and the process of the reference application are intended to be a coarseness of at least one denier and preferably 30 denier and larger. The process creates fibers having a variety of coarseness levels and that have approximately 10-30% of the fibers that are suitable for textiles. The desirable high coarseness fibers must then be extracted from the digested fiber mass for use in textiles.
Reference Application, U.S. #20070049661:
The reference relates to the use of soy and other annual crop straw and stalks for use in strandboard. The technology includes the step of de-pithing, cutting to length, drying and applying resin and wax to bind the fibers into the final strandboard product. No digesting or cooking of the fibers is involved. The straw and stalks are simply mechanically processed or steam treated into long bundles of fibers with little or no separation into smaller fiber cells.
Reference Application, U.S. #20080032147A1:
This reference relates to the use of annual crop fibers for Medium Density Fiberboard (MDF). The straw and stalks are steam treated to open the fibers enough to create fibers suitable for MDF manufacture. No digestion or bleaching or lignin removal is indicated.
Reference U.S. Pat. No. 6,492,574:
General reference to use of wheat straw as a source of cellulose for absorbent articles, but no mention of soy stalk fiber or any specific enabling technology for processing the wheat or fiber specific properties or dimensions.
Reference U.S. Pat. No. 5,705,216:
Describes process for steam treatment and extrusion of straw to make hydrophobic fibers suitable for injection molded plastics. The reference patent does not mention use of soy stalk fibers.
Reference U.S. Pat. No. 4,468,428, P&G:
This patent discloses use of wheat straw fibers and other micro-fibers having diameter of 0.5 to 10 microns and an absorbent pad density of 0.04 to 0.15 g/cc. for use in absorbent articles such as diapers.
Although the above indicated technologies have been used to produce fibers from annual crops, to date there have been none that are technologically, commercially and economically viable for use in paper and related products and none that have been suitable for use in absorbent products. Also, none have shown the appearance and color needed for certain paper, tissue and toweling, molded pulp products, paperboard, and absorbent products without chlorine bleaching which is environmentally undesirable and economically unfeasible.
Furthermore, these references do not disclose mixtures of soy and wheat fibers, which mixtures have surprisingly improved properties and value including but not limited to twice the available fiber (acres of crop) due to required crop rotation and more flexibility in fiber furnish that can be processed at the same operating conditions, requiring little or no process changes or adjustments. In order to maintain soil quality, soy is typically rotated with wheat every year, resulting in a field providing wheat or soy every other year. The mixtures also provide more pleasing color than each fiber alone and the mixtures provide improved processing for the Thermoformed Pulp process including more effective of water spray trimming and elimination of steam bubbles during the drying and molding step of the process associated with the use of 100% wheat straw fiber.